CONICET | Buscador de Institutos y Recursos Humanos

Although cerium oxide presents good oxygen storage capacity (OSC) and good redoxproperties, these properties could be improved by doping ceria with trivalent ions like Fe.Doping with alliovalent cations potentially increases the number of anion vacanciesimproving the oxygen mobility and the reducibility of the material. The resultant solid wouldbe a better material for catalytic applications. Samples with different iron content (Fe:[Ce+Fe] molar ratios= 0, 0.05, 0.1, 0.15, 0.20, 0.30 and 1) were synthesized by Citrates and Liquid-mix methods and calcined at 623K for 2h. The samples were named 0Fe, 5Fe, 10Fe, 15Fe, 20Fe, 30Fe and 100Fe, respectively. The structural changes during the reduction of the \ce{CeFeO_{\delta}} system was studied by ?in situ? X-ray powder diffraction (XPD), at the D10B-XPD beamline of the Brazilian Synchrotron Light Laboratory, at different temperatures, in an atmosphere containing 5%\ce{H_2}, using a high-intensity and low resolution configuration. The diffraction patterns were well resolved with high intensity thus allowing the use of Rietveld refinement method. At room temperature all cerium containing samples showed only the peaks corresponding to the fluorite structure of \ce{CeO_2}.However, sample 30Fe presented asymmetric peaks indicating thatsome kind ofinhomogeneity could exists. Sample 100Fe presented two phases with hematite-like and magnetite-like structures. At 623K sample 100Fe reduced to pure magnetite while nochanges were observed for cerium containing samples. At 923K, all samples excepting pure cerium oxide (0Fe) showed the presence of FeO (wustite). At 1073K, sample 100Fe showed only peaks associated to wustite phase while the mixed oxides presented the peaks corresponding to \ce{CeFeO_3} superimposed with those corresponding to the fluorite structure and very small peaks associated to wustite. No other cerium containing phases were observed during the experiments